Non-contact torque sensing for valve actuators

ABSTRACT

Non-contact torque, thrust, strain, and other data sensing of a valve actuator or valve is disclosed. A sensor may include a surface acoustic wave device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/070,184, filed Feb. 15, 2008, now U.S. Pat. No. 8,096,523, issuedJan. 17, 2012, which is a utility conversion of U.S. Provisional PatentApplication Ser. No. 60/902,029 for “NON-CONTACT TORQUE SENSING FORVALVE ACTUATORS” and claims the benefit of the filing date of Feb. 16,2007, the disclosure of each of which is hereby incorporated herein bythis reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to methods, systems, and devicesfor torque measurement and, more specifically, for non-contact torquesensing of a valve actuator.

BACKGROUND OF THE INVENTION

Valves include devices for both liquids and gases. Valve actuators forvalves are known and may be mechanically operated. For example, thevalve actuator may be manually driven, operated by fluid pressure inwhich the shaft is connected directly or indirectly to a fluid operatedpiston, or be driven by an electro-hydraulic or electro-fluid means.Conventional valve actuators comprise an electrically driven inputshaft, which may be rotatable at relatively high speeds with relativelylow torque. The input shaft may, through reducing gears such as a wormgear or a helical screw thread and nut, rotate a relatively high torque,low speed output shaft.

Actuators are often sized such that they can provide more torque thannecessary to fully seat a given valve. It may be desirable to determinethe torque generated by the output shaft or drive sleeve of a valveactuator. For example, when a valve is fully closed and seated, thetorque required to open the valve may be considerably higher.Consistently monitoring the torque may indicate if a valve is wearingout or sticking. Trending patterns in the torque measurements may enablepredictive maintenance.

Actuators need to control or limit the amount of torque that can beapplied to the load in a manner that is appropriate for variousoperating modes in a given application. Older mechanical technologiestypically operate in either of two modes: active or bypassed. If atorque threshold is exceeded, then the mechanical torque sensor switchesthe actuator into bypass mode. The torque threshold for switchingbetween modes is fixed by the user at startup and remains fixed untilphysically changed by the user.

Non-mechanical torque sensors may be used with rotary components;however, the torque sensors would need to be placed on a torsion elementin the drive train of the valve actuator. The drive train would bespinning during operation. Therefore, retrieval of the torqueinformation from the spinning sensor would be difficult.

It would be advantageous to develop a technique for measuring the torquegenerated by a valve actuator without the need to contact a rotatingmember of the valve actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a surface acoustic wave that may beused with embodiments of the present invention.

FIG. 2 is a cut-away view of one example of a valve actuator that mayutilize embodiments of the present invention.

FIGS. 3 and 4 illustrate sensor configurations in accordance withembodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention, butmerely as providing illustrations of some representative embodiments.Similarly, other embodiments of the invention may be devised that do notdepart from the spirit or scope of the present invention. Features fromdifferent embodiments may be employed in combination.

One embodiment of the present invention relates to mounting anon-contact sensor, for measuring torque or thrust, on a rotarycomponent of an electric valve actuator.

In a particular embodiment, a non-contact sensor includes a surfaceacoustic wave (SAW) device. A SAW device may be made up of amicrostructure deposited on a piezoelectric substrate. Themicrostructure may be formed by at least one pair of interleavedcomb-like electrodes deposited as a thin metal conducting layer on thesubstrate. FIG. 1 illustrates a basic exemplary model of a SAW device100 having input electrode 110 interleaved with output electrode 120.The electrodes 110 and 120 (referring to both input electrode 110 andoutput electrode 120) may include a deposit of aluminum, or otherconductors, on upper surface 140 of a piezoelectric substrate 130. In aparticular embodiment, the thickness of electrodes 110 and 120 may be onthe order of 1000 Angstroms. Many piezoelectric materials are suitablefor use as a substrate, including flexible plastic polymers and hardmaterials, such as ceramic and quartz. Various piezoelectric crystalforms may be used. Non-limiting examples of suitable materials includelithium niobate, lithium tantalate, bismuth germanlure oxide, andgallium oxide.

In SAW device 100, the application of an electric signal to inputelectrode 110 causes the electrode to act as a transducer converting theelectrical input signal into an outgoing acoustic wave on piezoelectricsubstrate 130. Output electrode 120 reverses the process providing anelectrical output signal with the arrival of an acoustic wave onpiezoelectric substrate 130.

The operational frequencies of SAW device 100 can be selected anywherein a wide frequency range extending from a few megahertz up to fewgigahertz. The higher the frequency used, the smaller the enveloperequired for the transducer (electrodes 110 and 120), which may bebeneficial where available space is limited. The resonant frequency useddepends on a number of factors including the geometry of the electrodes110 and 120 and the properties of piezoelectric substrate 130.Electrodes 110 and 120 may have any geometry and distance that isnecessary between them. The velocity of the surface wave varies with thetemperature of piezoelectric substrate 130. The very small sizes inwhich SAW device 100 can be made facilitate its use as a strainmeasuring device for a valve actuator.

Coupling between the electrodes 110 and 120 can be accomplished bysurface acoustic waves (also known as Rayleigh waves). Another acousticpropagation mode which can be used to couple electrodes 110 and 120includes surface skimming bulk waves. These extend more deeply intopiezoelectric substrate 130 than the surface acoustic waves and,consequently, the surface skimming bulk waves have higher losses thanarise with the surface acoustic mode. However, the bulk waves are lesssensitive to defects in upper surface 140. The choice of coupling wavemay be varied and may depend on the strain measurement to be undertaken.

SAW device 100 may be used in a system where signal inputs to atransducer input (electrode 110) and signal outputs from a transducer(electrode 120) are transmitted by non-contact coupling (such as byinductive, capacitative, or radio wave means) to an external controlsystem. The provision of a non-contact coupling where the electrodes 110and 120 have no direct electrical connection provides a number ofadvantages, particularly when there is a need for intrinsic safety orwhere physical connection would affect the resonance to be measured.Such non-contact systems are particularly convenient for rotatingcomponents of a valve actuator. A SAW device 100 may be used in place ofa resistive strain gauge. SAW device 100 may be capable of a degree ofaccuracy substantially greater than that of a conventional resistivestrain gauge. Electrodes 110 and 120 may take a number of forms, withsize and geometry of electrodes 110 and 120 capable of being modified toaffect operating frequency.

SAW device 100 may have a single port, two-ports, or multiple ports. Atwo-port type has lower losses than a corresponding single port type andmay be made to operate in a multi-mode fashion. Additionally, a two-porttype may have advantages with regard to phase shift, thereby providinghigher operational precision. Additionally, amplifiers may be used toincrease the signal generated by output electrode 120.

Torque (radial strain) may be measured by a change in the outputfrequency of electrode 120 arising from a change in the shape ofpiezoelectric substrate 130 and, thereby, in the relative positions ofthe electrodes 110 and 120. The radial strain may be induced by a stresson the member to be measured. The change in the output frequency ofelectrode 120 is proportional to the applied torque.

SAW device 100 may thus be utilized to measure either torque or axialthrust on rotatable components of a valve actuator. SAW device 100 maybe placed on a rotating component at an angle relative to the axis ofrotation, such that torque in one direction results in compression andtorque in the other direction results in tension. Two SAW devices 100may be placed at opposing angles to each other (either overlapping orotherwise) such that when one SAW device 100 is experiencing compressionthe other is experiencing tension, and vice-versa. Alternatively, oneSAW device 100 may be provided to measure axial thrust and a second SAWdevice 100 placed to measure torque. Any number of SAW devices 100 maybe used at a given location of a rotating component. Additionally, axialthrust of a rotating component may be used to calculate torque.

SAW device 100 may also be placed on a rotating component such that thedevice only experiences deformation when the rotating component isbending relative to the axis of rotation. Knowledge of such bending mayprovide more accurate torque calculations from the strain on other SAWdevices on the component. SAW device 100 may also be used for measuringthrust on stationary components of a valve actuator.

FIG. 2 depicts some embodiments of possible locations in an electricallydriven valve actuator where SAW devices 100 may be mounted. SAW devices100 may be mounted on worm shaft 3, motor drive shaft 9, drive sleeve 2,and handwheel adapter 11. SAW devices 100 also may be mounted on theteeth of worm gear 10 and worm shaft 3. SAW devices 100 may be mountedon declutch mechanism 13 or declutch handle 5. If an encoder 6 ispresent, SAW devices 100 may be mounted on an input shaft for theencoder 6. SAW devices 100 may be mounted on stationary components ofvalve actuator 20, including housing 4.

“Mounted on” as the phrase is used herein encompasses any form ofattaching, placing, integrating, embedding, housing, or inserting a SAWdevice. In one such exemplary embodiment, a SAW device 100 may be placedon a surface of a component. This may be accomplished, for example, viawelding or adhesives. In another embodiment, a SAW device 100 may beplaced in or integrated with a jacket or sheath and placed on thesurface. In a further embodiment, a SAW device may be integrated withanother device, and the device mounted upon the surface. In a particularembodiment, SAW devices 100 may be embedded in a component. In yetanother embodiment, SAW devices 100 may be fabricated in a component.For example, a piezoelectric material may be integrated into a componentwhen the component is manufactured and conductors for the electrodeslater deposited on the piezoelectric material.

SAW devices 100 may be located throughout valve actuator 20. In oneembodiment, differences between the torques of various components may beindicative of component wear and provide an early warning of maintenanceissues.

Valve actuator 20 is a non-limiting example of a valve actuator that mayuse SAW devices 100. Valve actuator 20 may be any type of electricallydriven valve actuator. For example, valve actuator 20, instead of usinga drive sleeve 2, may have an output shaft.

Valve actuator 20 does not need to be electrically driven. Handwheel 1represents one exemplary embodiment of how valve actuator 20 may bemanually operated. Additionally, valve actuator 20 may also be partiallypneumatically and/or hydraulically actuated.

SAW devices 100 may also be mounted on the rotatable or stationarycomponents of a valve. In a particular embodiment, SAW devices 100 aremounted on a valve stem. SAW devices 100 may be used to monitor torqueexperienced by a rotating valve stem or axial thrust experienced by alinear moving valve stem. Any component of a valve, such as the paddleof a butterfly valve, may have SAW devices 100 mounted thereon.

Any necessary electronics may be attached to, or proximally located by,a SAW device 100. Where induction or capacitance are used to power SAWdevices 100, the excitement sources may need to be relatively close toSAW devices 100. Wireless exciters may utilize radio frequencies toexcite input electrodes 110. Wireless receivers may be designed toreceive radio frequency outputs from output electrodes 120. Wirelessexciters/receivers may be designed for continuous or intermittentoperation. “Wireless exciters/receivers,” as the phrase is used herein,encompass both an embodiment where the exciter is separate from thereceiver and an embodiment where both functions are accomplished by asingle device. Wireless exciters/receivers may be built into or beexternal to valve actuator 20. In a particular embodiment, wirelessexciters/receivers are built into control module 8 or circuit board 15.Where wireless exciters/receivers are built into the valve actuator 20,SAW devices 100 may be activated using control panel 7 or from a remotecontrol station. Torque, thrust, or strain values may be indicated ondisplay 12 and/or transmitted to a remote location.

In other embodiments, a wireless exciter/receiver may be built into apersonal digital assistant (PDA), laptop, or other portable device. Theappropriate software may be included to compute a torque, thrust, orstrain based upon the signal outputted by SAW devices 100. In anotherembodiment, wireless exciter/receiver nodes may be located in thevicinity of multiple valve actuators and valves. The wirelessexciter/receiver nodes could transmit torque and other data for numerousvalve actuators and valves to a central control station. The wirelessexciter/receiver nodes may be designed to transmit data not obtainedfrom SAW devices 100 as well.

Where SAW devices 100 are found in multiple locations in a valveactuator 20, torque data may be uniquely identified by location.Similarly, where multiple valve actuators 20 or valves are externallywirelessly excited, torque data may be uniquely associated with aparticular valve actuator 20 and/or locations within the actuator.Unique identification may be accomplished in a number of ways.

In a particular embodiment, the signal transmitted by a SAW device 100may be unique. Therefore, two SAW devices 100 experiencing the samestrain would transmit different outputs. In one embodiment, differentSAW devices 100 could utilize different input frequencies. The inputfrequencies could be sufficiently different so that, regardless of anystrain experienced, the output frequency range of each SAW device 100would not overlap. In a second embodiment, reflectors may be placed inpiezoelectric substrate 130 to modify the output frequency. Each SAWdevice 100 may have a unique set of reflectors. The reflectors may beplaced such that torque data may be obtained and then determine whichparticular SAW device 100 is transmitting.

In another particular embodiment, any electronics associated with a SAWdevice 100 may provide unique identification of a SAW device 100 orgroup of SAW devices 100 at one location. In one embodiment, anamplifier for each SAW 100 device may provide a unique level ofamplification, thereby distinguishing the SAW device 100. In a secondembodiment, a unique converter may be associated with each SAW device100. The unique converter could alter the signal type produced by anoutput electrode 120. Therefore, the new unique signal type couldidentify the source SAW device 100. In a third embodiment, a uniquewireless tag can be added to the output produced by output electrode 120to uniquely identify the source.

In yet another embodiment, a wireless exciter/receiver may be used touniquely identify a SAW device 100. In one variation of the invention,only one valve actuator 20 at a time may be subjected to transmissionfrom the wireless exciter/receiver. For example, a PDA having only alow-power exciter could be directed at a specific valve actuator 20. Ina second embodiment, the intensity of transmission from a SAW device 100may be used to identify its location. For example, assuming all of theamplifiers are equal, the distance from a SAW device 100 to a wirelessexciter/receiver will determine the strength or intensity of the signalreceived by the wireless exciter/receiver. The intensity of each signalmay be measured. If each of the SAW devices 100 is at sufficientlydifferent distances from the wireless exciter/receiver, then thedifferent intensities of signals may be used to identify the sources.Any other means in the art for identifying the source of radiofrequencies may be used.

SAW devices 100 may be utilized for generating torque, thrust, strain,temperature, pressure, speed, position, and other data.

Embodiments have been described using a SAW device. It should beunderstood that any non-contact sensing may be used in place of the SAWdevice. For example, other embodiments of a non-contact sensor may usemagnetoelasticity, magnetostriction, stress wires, “guitar string”elements, strain gauges, acoustics, light, optics, capacitance,inductance, resistance, reluctance, radio telemetry, strain members,charge coupled devices, or micromachining to make a non-contactdetermination of the torque of a rotating component.

As shown in FIG. 3, in one embodiment of a non-contact torque sensor,strain gauges 200 attached to a rotary component 50 may be powered by abattery attached to the rotary component 50 and the output of the straingauges 200 (or an equivalent) wirelessly transmitted.

As shown in FIG. 4, one embodiment of a non-contact optical sensorutilizes two optical sensors 300 placed in line on a rotary component 50relative the rotational axis of the component 50. As the rotarycomponent twists under torque, the two optical sensors will no longer bein line. The displacement between the two sensors may be used todetermine the torque experienced.

A non-contact sensor may be passive and not require a battery or someother external power source. In other embodiments, the non-contactsensor may be active and require an external power source.

Although the foregoing description contains many specifics, these arenot to be construed as limiting the scope of the present invention, butmerely as providing certain representative embodiments. Similarly, otherembodiments of the invention can be devised which do not depart from thespirit or scope of the present invention.

What is claimed is:
 1. An electric valve system, comprising: an electricvalve actuator; a valve; a rotating member; and a sensor comprising atleast one surface acoustic wave device, the at least one surfaceacoustic wave device attached to the rotating member, wherein the atleast one surface acoustic wave device outputs a uniquely identifiablesignal to a wireless receiver, wherein the surface acoustic wave deviceis configured to measure one or more of a torque and an axial thrustassociated with the rotating member.
 2. The valve actuator of claim 1,wherein the at least one surface acoustic wave device comprises twosurface acoustic wave devices placed at opposing angles to each other onthe rotating member.
 3. The valve actuator of claim 1, wherein the atleast one surface acoustic wave device measures axial thrust.
 4. Thevalve actuator of claim 1, wherein the at least one surface acousticwave device measures torque.
 5. The valve actuator of claim 1, whereinthe rotating member is selected from the group consisting of a valvestem, worm shaft, motor drive shaft, drive sleeve, handwheel adapter,teeth of worm gear, declutch mechanism, declutch handle, and input shaftfor an encoder.
 6. The valve actuator of claim 1, wherein the sensorcomprises a plurality of surface acoustic wave devices and wherein eachsurface acoustic wave device of the plurality of surface acoustic wavedevices outputs a uniquely identifiable signal to a wireless receiver.7. The valve actuator of claim 1, wherein the at least one surfaceacoustic wave device comprises a first surface acoustic wave device thatoutputs a uniquely identifiable wireless signal within a first frequencyrange and a second surface acoustic wave device that outputs a uniquelyidentifiable wireless signal within a second frequency range wherein thesecond frequency range does not overlap the first frequency range.
 8. Anelectric valve system, comprising: an electric valve actuator; a valve;a rotatable component of the electric valve actuator or valve; and atleast one non contact sensor operably mounted on the rotatablecomponent, the at least one non contact sensor configured to generatetorque or thrust data, wherein the at least one non contact sensoroutputs a uniquely identifiable signal to a wireless receiver, whereinthe at least one non contact sensor comprises at least one surfaceacoustic wave device.
 9. The electric valve system of claim 8, whereinthe at least one surface acoustic wave device measures axial thrust. 10.The electric valve system of claim 8, wherein the at least one surfaceacoustic wave device operates at a frequency range of about 3 megahertzto about 3 gigahertz.
 11. The electric valve system of claim 8, whereinthe at least one surface acoustic wave device comprises two surfaceacoustic wave devices placed at opposing angles to each other on therotatable component.
 12. The electric valve system of claim 8, whereinthe at least one surface acoustic wave device comprises a first surfaceacoustic wave device that outputs a uniquely identifiable wirelesssignal within a first frequency range and a second surface acoustic wavedevice that outputs a uniquely identifiable wireless signal within asecond frequency range wherein the second frequency range does notoverlap the first frequency range.
 13. The electric valve system ofclaim 8, further comprising a display that indicates output valuesassociated with the at least one surface acoustic wave device.
 14. Anelectric valve system, comprising: an electric valve actuator; a valve;a rotatable component of the electric valve actuator or valve; and aplurality of non contact sensors operably mounted on the rotatablecomponent and configured to generate torque or thrust data, theplurality of non contact sensors comprising: a first non contact sensorthat outputs a uniquely identifiable wireless signal within a firstfrequency range; and a second non contact sensor that outputs a uniquelyidentifiable wireless signal within a second frequency range wherein thesecond frequency range does not overlap the first frequency range. 15.The electric valve system of claim 14, wherein the plurality of noncontact sensors comprises strain gauges attached to the rotatablecomponent.
 16. The electric valve system of claim 14, wherein the atleast plurality of non contact sensors comprises two optical sensorsplaced in line on the rotatable component relative to a rotational axisof the rotatable component.
 17. The electric valve system of claim 14,wherein the rotatable component is selected from the group consisting ofa worm shaft, motor drive shaft, drive sleeve, handwheel adapter, teethof worm gear, declutch mechanism, declutch handle, and input shaft foran encoder.
 18. The electric valve system of claim 14, wherein therotatable component is a valve stem.
 19. The electric valve system ofclaim 14, wherein the plurality of non contact sensors comprises aplurality of surface acoustic wave devices and wherein each surfaceacoustic wave device of the plurality of surface acoustic wave devicesoutputs a uniquely identifiable signal to a wireless receiver.
 20. Theelectric valve system of claim 14, wherein the rotatable component is alinear moving valve stem.